Moon Mirrors Imagined
GREENBELT, Md., June 5, 2008 -- An innovative recipe for giant telescope mirrors on the moon has been concocted by scientists working at NASA’s Goddard Space Flight Center in Greenbelt, Md.
To make a mirror that dwarfs anything on Earth, just take a little bit of carbon, throw in some epoxy, and add lots of lunar dust.
"We could make huge telescopes on the moon relatively easily and avoid the large expense of transporting a large mirror from Earth," said Peter Chen of NASA Goddard and the Catholic University of America, in Washington, D.C. "Since most of the materials are already there in the form of dust, you don't have to bring very much stuff with you, and that saves a ton of money."
Chen and his Goddard colleagues Douglas Rabin, Michael Van Steenberg and Ron Oliversen presented their mirror-making technique in a poster session at the 212th meeting of the American Astronomical Society, being held this week in St. Louis, Mo.
This image of the moon was taken from the command module of Apollo 12 after it left lunar orbit on Nov. 24, 1969. (Photo courtesy NASA)
For years, Chen had worked with carbon-fiber composite materials to produce high-quality telescope mirrors. But he and his colleagues decided to try an experiment: They substituted carbon nanotubes (tiny tubular structures made of pure carbon) for the carbon-fiber composites. When they mixed small amounts of carbon nanotubes and epoxies (glue-like materials) with crushed rock that has the same composition and grain size as lunar dust, they discovered -- to their surprise -- that they had created a very strong material with the consistency of concrete. This material can be used instead of glass to make mirrors.
Next, they applied more epoxy layers and spun the material at room temperature. The result was a 12-in-wide mirror blank with the parabolic shape of a telescope mirror. (All of this was achieved with minimal effort and cost.)
"After that, all we needed to do was coat the mirror blank with a small amount of aluminum, and voilà, we had a highly reflective telescope mirror," said Rabin. "Our method could be scaled-up on the moon, using the ubiquitous lunar dust, to create giant telescope mirrors up to 50 meters in diameter." Such an observatory would dwarf the largest optical telescope in the world right now, the 10.4-m Gran Telescopio Canarias in the Canary Islands.
The capabilities of a 50-m telescope on the Moon boggle the imagination, NASA said in a statement. With a stable platform, and no atmosphere to absorb or blur starlight, the monster scope could record the spectra of extra solar terrestrial planets and detect atmospheric biomarkers such as ozone and methane. Two or more such telescopes spanning the surface of the Moon can work together to take direct images of Earth-like planets around nearby stars and look for brightness variations that come from oceans and continents. Among many other projects, it could make detailed observations of galaxies at various distances, to see how the universe evolved.
"Constructing giant telescopes provides a strong rationale for doing astronomy from the moon," Chen said. "We could also use this on-site composite material to build habitats for the astronauts and mirrors to collect sunlight for solar-power farms."
Chen said his group achieved this breakthrough with only the support of small NASA internal seed funds. The carbon nanotubes were contributed by Dan Powell, lead nanotechnologist for NASA Goddard. Several amateur astronomers made key contributions by advising and making special epoxy formulations, helping with polishing experiments, and vacuum-coating the 12-in mirror.
For more information, visit: www.nasa.gov/centers/goddard
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